Within an aircraft, an oil system is frequently used. Oil is used for cooling and lubricating various aircraft entities, such as rotating shaft bearings, a fan drive gear system, and a gearbox, where the gearbox extracts power from an engine for purposes of driving generators, pumps, and auxiliary components/devices. The oil system includes a tank for storing bulk oil and pipes that connect the tank to the various entities that require the oil.
A cooler may be used to remove heat from the oil. An air-oil cooler uses air for purposes of providing a cooling fluid. For example, air is taken from the fan bypass, flowed through the cooler, and returned to the fan bypass as an exhaust.
Foils located in the cooler are fragile, such that the foils are susceptible to damage if subjected to a direct impact from large objects (e.g., hail stones). Measures need to be taken to ensure that the foils are not damaged; otherwise, the reliability and availability of the aircraft may be compromised.